I was reluctant to invest in a REAL spot welder. I scoured youtube for some freak gadget that would actually work. I got this.
I watched as youtubers put the peddle to the metal, and blew them up. I read warnings and found, that most blew it up with undervolted use.
And so, I used my reconfigured headway batt in 12v mode. I used it with only enough juice to make good welds. It worked a charm. The only thing is, you have to keep feeling the unit, and space your use to keep it warm, not hot. The duty cycle is the only thing that makes this choice worse than a sunnko etc. And, I didnt have to shell out for a hand rig.
So, if you are faced with building a batt, and dont want to fear your 110 being inadequate, or going 220v, and being tied to the dryer plug, this is a fully adequate solution.
Just remember, have a PROPER power source, and watch your duty cycle and SPOT ON.